Rheostat.



L. L. TTUM.

RHEOSTAT.

APPLICATION FILED F5310. 1913.

Ll 12J 76g Patented Sept. 29, 1914.

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@aw/w @5mm/vw UNITED srATns LEWIS L. 'TA.TUM,- v0F MILWUKEE, WISCONSIN, ASSIGNOR T THE CUTLEt-HAMMEE MFG. G., 0F MILWAUKEE, WISCNSIN, A COREORATIGN 0F WISCONSIN.

RHEOSTAT.

To all whom "it may concern Be it known that I, LE-wrs L. TATUM, a citizen yof the United States, residing at Milwaukee, in the county of Milwaukee and State of Wisconsin, have invented new and useful Improvements in Rheostats, of'which the following is a full, clear, concise, and exact description, reference being had to the accompanying drawing, forming a part of this specication.

My invention relatesto improvements in rheostats and more particularly to rheostats in which the resistance thereof is mounted in or upon a heat absorbing body. Such rheostats are used for various different urposes vand are very commonly use in theater dimmers.l In the rheostat plates of theater dimmers, and also' of various other forms of controllers, it has been customary to portion off the surface" of the supporting base or plate into circuit the current in the preceding steps is reduced with a corresponding reduction in the heat dissipated thereby.` Thus in oper-- ation a large portion of the base or plate available for heat absorption is practically inactive or at least only utilized to a small degree of its maximum capacity.

My invention has for-one of its objects to provide a rheostat structure wherein a heat absorbing base of a given size may be utilized to absorb the heat of a materially greater amount of resistance without at any time overtaxing the capacity of any portion thereof.

A ,further object is to produce a duplex rheostat in which each section thereof will utilize for. heat dissipation the availablel Specicaton of Letters Patent.

Application sled IFebruary 1o, 1913.

Patented Sept. 29, 1914.

serieu No. 747,420.`

tion at such point by a single section. The advantages of such a rheostat are at once obvious. For example, it provides for economy of material and economy of space, both of which are very important features in rheostats.

Various other objects and advantages of my invention will hereinafter appear. l In order to morel fully and clearly disclose the nature and advantages of my invention I shall describe the rheostat illustrated in the accompanying drawing, which embodies my invention in one form. yIt should,vof course, be understood that my invention might be embodied iu other forms having all the advantages of the form selected for illustration.

In the drawing, Figure l is an elevation of the rheostat; and, Figs. 2 and 3 are views of opposite sides thereof.

The rheostat selected for the purpose of illustration is one particularly adapted to use in theater dimmers but, of course, it might be usedin other relations. Briefly described, it comprises two substantially identical sets of resistances 1, la, and 2, i2, mounted upon opposite sides of a common supporting plate or base 3 of suitable heat absorbing capacity. The sets of resistances l, la, and 2, 2a, are provided with separate controlling elements l and 5 respectively,

and, as will be' hereinafter more fully set forth, the resistances are arranged in such relation on the baseas to cause each to utilize for heat, dissipation that portion of the base which is not utilized, or at least not utilized to its full capacity, by the other resistance, and to insure against the heating of any portion of the base to any materially greater extent than it would be heated by a single resistance under maximum heat conditions at that\portion.

In practice' any preferred form of base and resistance may be employed and the resistance may'be mounted upon the base in any preferred manner. As illustrated, the base is of circular form with the sets of resistances embedded in the opposite faces thereof. rlhe base?) is preferably formed of soapstone or-other non-conducting heat absorbing material. The resistances prefand 5 each comprise a single conducting bar' fulcrumed upon a spindle 12 concentric with the arcs of the contacts and each is provided at opposite ends with brushes adapted to engage dia-metrically opposite contacts on one side of the base.

Referring to Figs. 2 and 3 it will be ,'observed that the circuit connections are such that each arm when moved in one direction will increase both sections of its respective set of resistances and when moved in the opposite direction will decrease both sections thereof. Further referring to Figs. 2 and 3 it will be observed that' the line of division between the resistance sections l and 1L is perpendicular to the ,line of division between the resistance sections 2 and 2a. Accordingly, the controlling elements 4 and 5 wh en in corresponding positions with respect to their individual resistances will be 90 apart. Hence, if both controlling elements be moved simultaneously the resista-nce sections inserted in circuit thereby will be 90O apart and they will dissipate heat to portions of the base 90o apart. case. each will. dissipate heat to that section of the base which is inactive with respect to the other set of resistances and this same condition will prevail for 90 rotation. Continued rotation will then cause gradual insertion of resistance directly opposite the previously inserted resistance on the. other side of the base. Under such ccnditions the opposite sections of resistance will tra-nsmit heat to the same portions of the base. As before stated.y however. the rate of heat dissipation by the individual steps of resistance is decreased by the insertion in circuit of subseouent steps of resistance. Accordingly. with the resistance arranged as fllescribed. it will .be obvious that when two opposite steps of resistance are inserted 1n circuit one section will be dissipating' heat at a materially reduced rato so that the total amount of heat dissipated by the two sections will not be excessive.

Theadvantages of the above described arrangement increase as the adjustable resistance of the controlled circuit is increased relatively to the iixed resistance thereof. This is because an increase between the adjustable and fixed 'resistance increases the Such being the range of heat vdissipation to the differs portions of the base, and thus increases area of the base which is inoperative or worked below maximum capacity.

As an example of the range of heat .f'aria-e tion, letit be assumed that it is desired. to regulate a bank of lamps having a resistance of 5 ohms on a 100 volt circuit by a rheostat or dimmer resistance of 15 ohms, the resistance being arranged in steps of such value that the maximum value of atts dissipated in each step shall be the flame.

1f R is the ohmic value of the first sep of resistance to be cut into circuit, then the maximum watts dissipated on that step will be the square of the maximum current times the resistance, or approximately 202 .i or L1-00 R. lVhen all the resistance is in A'circuit the current is reduced to 5 amperes but 'since the value R on the step remains unthe other side of the base without the sum `of the two exceeding safe value.

That 1 claim as new lnd desire to secure by Letters Patent is:

l. A rheostat comprising a heat absoiir ing base, and adjustable resistances mounted onl opposite sides thereof with their successive steps in relatively different positions with respect to said base.

2. A rheostat comprising a heat absorbing base, adjustable resistances mounted on opposite sides thereof to transmitheat thereto. the steps of resistauces at corresponding points on opposite sides of the base being separated from their respective terminals by resistaneesof different values.

A rheostat comprisingl two resistances, and a common supporting base therefor arranged between the same. said resistances being arrangerLv in different relations with resiiect to said base wherel'u.7 when both re-1 sistanres transmit heat to the same portion or portions of the base the rate of heat lis sipa'tion of one resistance will be red 4. A rheostat comprising` two a Q resistances, a common supporting base therefor arranged" between the same to absorb heat therefrom.y said resistances being of dierent ,f'alues between their respective terminals and corresponding points on opposite sides of said base throughout their respective lengths.'

'5. A rheostat comprising a heat absorbing base, resistances mounted on opposite sides throf, and conm-@Ring eemms winess whereof, have hereunto submoune @n oppnsvb sides of said has@ im ScrbQ-. my mun@ in the presence of two witachustmg Sad eslstancesi sind elmemts sses.

`hroughollt their entire 'range of movement y 'LEWS L. TTUM. having 1i'erent relative post'mhs for cor- Witnesses:

" respondmg contcol of `their respective re- F. H. HUBBARD,

Simancas. H. WATSON. 

